In an internal combustion engine equipped with a control apparatus for a supercharger equipped with a variable flow rate mechanism being capable of controlling an intake air amount and an intake air pressure to a combustion chamber and a control apparatus for an exhaust gas recirculation apparatus (EGR) for recirculating a part of the exhaust gas to an intake-air passage or a cylinder, such as a diesel engine, in order to compensate for deficiency of the flow rate of the air entering the cylinder when the EGR is operating, by throttling a guide vane of the variable flow rate mechanism forming the supercharger (e.g. VFT) equipped with the variable flow rate mechanism, the exhaust gas pressure increases and in response to this, a recirculation amount of the exhaust gas recirculated by EGR increases. This makes it difficult to secure the amount of the air introduced into the combustion chamber or the intake oxygen concentration, thereby increasing black smoke occurrence. Alternatively, by opening the guide vane of the variable flow rate mechanism, the exhaust gas pressure declines, and this makes it difficult to secure the recirculation amount of EGR gas and to obtain NOx reduction effect, etc. As described above, the control for the EGR and the control for the supercharger equipped with the variable flow rate mechanism have a relationship of mutual interference that affects each other.
Particularly, when a load torque is increase, i.e. in transition, the guide vane of the variable flow rate mechanism of the VFT is moved toward a closed state to secure the air flow rate. As a result, the exhaust gas pressure increases, the recirculation amount of the EGR gas becomes more than necessary, the air amount and the intake oxygen concentration declines, and occurrence of black smoke becomes evident.
As a cooperative control between the control for the EGR and the control for the supercharger equipped with the variable flow rate mechanism, the technique disclosed in JP2003-21000A (Patent Document 1) is known. In JP2003-21000A, a target air amount and a target supercharging pressure are individually set, and when calculating EGR valve deviation amount, not just a difference between a detection value of an intake amount sensor and a target air amount but a difference between a detection value of an intake pressure sensor and a target air pressure are taken into account. Further, when calculating a deviation amount of the variable geometry mechanism (VGT) of the supercharger, not just a difference between the detection value of the intake pressure sensor and the target supercharging pressure but a difference between the detection value of the intake air amount sensor and the target air amount are taken into account so as to control the EGR valve and the VGT in a cooperative manner.
Further, disclosed in JP2010-249057A (Patent Document 2) is to control the internal combustion engine by means of a 2-input, 2-output integral-type optimal servo system by inputting detection values of the air flow amount and the intake air pressure and controlling opening of the EGR valve and opening of the guide vane of the variable nozzle turbine, and also to change a state feedback gain KF(h) and an integrating gain KI(h) of the integral-type optimal servo system according to operation conditions h of the internal combustion engine.